Сегодня на улице так пасмурно, что мне хочется остаться дома.

Because пасмурно here is not describing a noun. It is being used in an impersonal weather expression, meaning something like it is overcast / gloomy.

Russian often uses short, neuter-looking forms like this for weather and general states:

• Холодно. = It is cold.
• Темно. = It is dark.
• Пасмурно. = It is overcast.

So in this sentence, на улице так пасмурно means outside it is so gloomy / overcast, not the street is gloomy.

Literally, yes, на улице means on the street or outside on the street. But in everyday Russian it very often simply means outside.

So:

• Сегодня на улице так пасмурно... = Today it’s so overcast outside...

It does not necessarily mean the speaker is standing in the street. It is just a common way to talk about the weather outdoors.

Because на here takes the prepositional case when it means location.

• улица = street
• на улице = on the street / outside

This is the normal pattern:

• на столе = on the table
• на работе = at work
• на улице = outside / in the street

So улице is the prepositional singular form of улица.

This is a very common Russian structure meaning so ... that ...

In your sentence:

• так пасмурно = so overcast
• что мне хочется остаться дома = that I feel like staying home

So the full pattern is:

• так + adverb/adjective + что + result

Examples:

• Он так устал, что сразу заснул. = He was so tired that he fell asleep immediately.
• Было так холодно, что мы не вышли. = It was so cold that we didn’t go out.

Мне хочется is an impersonal way to say I feel like or I have a desire to. It sounds softer, less direct, and often more natural for temporary feelings.

Compare:

• Я хочу остаться дома. = I want to stay home.
• Мне хочется остаться дома. = I feel like staying home.

So хочется is often used for a passing mood or desire, especially with things like weather, comfort, food, and emotions.

Because хочется is part of an impersonal construction. The person who experiences the feeling goes into the dative.

So:

• мне хочется = to me it is wanted, more naturally I feel like
• тебе хочется = you feel like
• ему хочется = he feels like

This is similar to other Russian impersonal patterns:

• мне холодно = I am cold
• мне грустно = I am sad
• мне нравится = I like

Russian does not need a dummy subject like English it.

In English, we say:

• It is cold
• It seems
• I feel like...

In Russian, many expressions are simply impersonal, with no subject at all:

• Холодно.
• Темнеет.
• Мне хочется спать.

So there is no hidden word corresponding to English it. The sentence is just built differently.

Because остаться is the perfective form, meaning to stay / remain as a complete decision or result.

Here the speaker means I feel like staying home, in the sense of remaining at home instead of going out. Russian often uses the perfective infinitive after хочется when talking about a single intended action or result.

Compare:

• остаться = to stay, to remain, to end up staying
• оставаться = to be staying, to stay habitually or over a period of time

In this sentence, остаться дома sounds natural because it refers to one situation today.

Because дома means at home, while домой means homeward / to home.

• остаться дома = to stay at home
• идти домой = to go home
• вернуться домой = to return home

Since the idea is stay at home, not go home, Russian uses дома.

Yes, literally it is closer to remain at home. In natural English, though, we usually say stay home or stay at home.

So:

• мне хочется остаться дома = I feel like staying home

The Russian verb emphasizes not going out or remaining at home.

Yes. Russian word order is fairly flexible, although the original order sounds natural and neutral.

Original:

• Сегодня на улице так пасмурно, что мне хочется остаться дома.

Possible variations:

• На улице сегодня так пасмурно, что мне хочется остаться дома.
• Мне хочется остаться дома, потому что сегодня на улице так пасмурно.

The original version is good because it starts with the time word сегодня, then sets the scene на улице, then gives the result.

No, it is not grammatically required. It just anchors the sentence in time.

• На улице так пасмурно, что мне хочется остаться дома.
  = It’s so overcast outside that I feel like staying home.

• Сегодня на улице так пасмурно...
  = Today it’s so overcast outside...

Without сегодня, the sentence becomes more general or just focused on the current moment without explicitly saying today.

Not in the same structure.

Here, что belongs to the pattern так ..., что ... = so ..., that ...

• Сегодня на улице так пасмурно, что мне хочется остаться дома.

If you want to use потому что = because, you need to restructure the sentence:

• Мне хочется остаться дома, потому что сегодня на улице пасмурно.

Both are correct, but the meaning emphasis is slightly different:

• так ..., что ... emphasizes the result
• потому что emphasizes the reason

It usually means overcast, gloomy, or dreary. It is often stronger and moodier than just plain cloudy.

So depending on context, it could suggest:

• cloudy
• overcast
• gloomy
• dreary

That is why the second half of the sentence feels natural: the weather is gloomy enough to make the speaker want to stay home.

Yes, very natural. It sounds like normal spoken or written Russian.

A native speaker could easily say this about bad weather. The sentence combines several very common patterns:

• на улице for outside
• weather word пасмурно
• так ..., что ...
• мне хочется + infinitive
• остаться дома

So it is a very useful model sentence to learn from.